This invention relates to a collapsible structure which can be suitable for use in building construction and to a method of building using such a structure.
With present day building methods, and in particular the provision of concrete floors on the ground floors of houses, considerable trouble has occurred where such floors are laid onto subsoils which are predominantly of a clay nature. The problem which arises depends upon the fact that clay will swell when moisture is introduced and will shrink when moisture is removed. In the case of clay situated under a house, the difference in level between dry clay and wet clay can be as high as 30 mm.
Thus, variations in the condition of the clay can have a very serious effect on any flooring material which is laid directly thereon, and when this flooring material is in contact with walls, the variations can cause severe damage to the building to which it belongs. In fact, this damage can be so severe that the building has to be demolished as being uneconomical to repair.
In order to overcome this problem it has been proposed to provide precast floor elements which can be mounted in position leaving a void between the underside and the ground. However, this process is of a very costly nature because, in most instances, it necessitates the transport of large concrete blocks and the provision at the site of a relatively large crane in order to unload the concrete elements and to place them in their appropriate position. As a result, other means have been tried to introduce between the floor and the clay a material which is sufficiently compressible to allow the movement of the clay to take place but of sufficient strength to form a firm base for the casting of the appropriate floor. Such proposals have included expanded polystyrene, ash and uncompacted sand. However, these have not proved satisfactory since where they are strong enough to support the load during casting of a concrete floor, they are insufficiently compressible to allow for full expansion and contraction of the clay and vice versa.